Enhance CI Workflow for Coverage Reporting

### Added
- Upload coverage artifact after tests.
- Download all coverage artifacts for reporting.

### Changed
- Updated Codecov action to version 4 and adjusted parameters for artifact directory.

Author: Artemonim

.github/workflows/ci.yml

@@ -48,8 +48,30 @@ jobs:
               run: |
                   pytest --cov=agent_docstrings --cov-report=xml --cov-report=term-missing
 
+            - name: Upload coverage artifact
+              uses: actions/upload-artifact@v4
+              with:
+                  name: coverage-${{ matrix.python-version }}-${{ matrix.beta }}
+                  path: coverage.xml
+
+    report:
+        name: Report Coverage
+        runs-on: ubuntu-latest
+        needs: test
+        steps:
+            - name: Checkout repository
+              uses: actions/checkout@v4
+
+            - name: Download all coverage artifacts
+              uses: actions/download-artifact@v4
+              with:
+                  path: coverage-artifacts
+                  pattern: coverage-*
+                  merge-multiple: true
+
             - name: Upload coverage to Codecov
-              uses: codecov/codecov-action@v3
+              uses: codecov/codecov-action@v4
               with:
-                  files: coverage.xml
+                  token: ${{ secrets.CODECOV_TOKEN }}
+                  directory: ./coverage-artifacts/
                   fail_ci_if_error: true